Not applicable.
The present invention relates in general to the provision of broadband services using a Digital Subscriber Loop (DSL) platform and, in particular, to a network service model that supports transparent QoS using VC-merge capable access modules, for delivering broadband services to Customer Premise Equipment (CPEs).
As traffic volume on the Internet continues to rapidly expand, the demand for bandwidth-intensive applications is also increasing. Demand for higher bandwidth, in turn, requires higher forwarding performance (packets per second) by routers, for both multi-cast and unicast traffic. Multicast services distribute, for example, news, entertainment or educational content, which is transported over the network from source nodes to a plurality of sink nodes. The source nodes are typically multicast servers, such as an Internet Protocol (IP) server connected to an IP multicast data network. The sink node, or CPE, is typically an end user""s communication device, such as, a personal computer (PC) connected to the network via a modem.
For high bandwidth applications, the use of high-speed Digital Subscriber Line (DSL) technology, cable modems, satellite systems, and the like, are becoming increasingly popular as a means of coupling Customer-Premise Equipment (CPE), such as personal computers or Local Area Network (LAN) servers with the communications network. DSL provides access to the Internet through a high speed Asynchronous Transfer Mode (ATM) access network, facilitating high bandwidth data transfer and providing for the possibility of application integrated quality of service.
Multicast data from a source node is typically routed to the ATM access network through an Internet Protocol (IP) Service Gateway (SG). Each Customer Premise Equipment (CPE) is normally connected to the ATM access network via an access module (e.g., a Digital Subscriber Loop Access Multiplexer (DSLAM), a cable headend, a wireless headend, a satellite base station, an optical line termination or an ATM side of the CPE).
Requests for the same multicast information, originating from two or more participating CPEs served by the same access module, results in multiple copies of the multicast data being routed through the ATM access network between the Service Gateway (SG) and the access module. This can cause degradation of performance due to bandwidth exhaustion and places an unreasonable burden on the Service Gateway (which typically performs complex packet inspection functions not required for streaming media). Furthermore, the QoS associated with the VCs serving the respective CPEs for basic service is inherited by the multicast packets affecting the rate of transfer of the packets across the ATM access network, and degrading the performance such that expected service levels cannot be sustained.
In order to overcome this problem and to reduce the duplication of traffic within the ATM access network, it is desirable to use additional ATM VCCs to augment basic connectivity to the service gateway for the transport of specific services. These are in the form of p2p connections between ATM attached content servers for unique services and ATM point-to-multipoint (p2mp) connections for multicast services. Similarly to minimize the complexity deployed in the subscriber end systems VCs are merged together or PDU interleaved using various methods known in the art. This permits dynamic xe2x80x9cper servicexe2x80x9d QoS to be extended to end systems that do not support ATM call processing.
In Applicant""s co-pending U.S. patent application Ser. No. 09/648,610, filed on Aug. 28, 2000 and entitled IP MULTICAST SERVICES OVER ATM MULTICAST, a method for grafting a sink node (leaf) to an Internet Service (multicast tree) created by the Service Gateway is described. The Service Gateway establishes a special virtual connection between the two through the ATM network when there are requests from various CPEs for particular multicast data. Duplication of multicast data traffic through the ATM network is thereby reduced and performance is improved.
When a Service Gateway receives messages from a plurality of sink nodes (i.e. CPEs) requesting the same multicast data, the Service Gateway identifies the appropriate access module and the CPEs are then grafted to the multicast tree at the access module. The access module performs a VC-merge operation to merge or PDU interleave the multicast data into a Virtual Channel Link (VCL) that is typically (but is not required to be) the CPE to access a node link component of a Virtual Channel Connection (VCC) connecting the CPE to the Service Gateway. Consequently, only one copy of the multicast traffic traverses the ATM access network between the service gateway and the access module, while a plurality of CPEs may be joined to the multicast tree at the access module. Similarly the network topology as viewed from the CPE is unchanged as the topology optimizations performed by combining multicast with merge are effectively transparent to the CPE. Once this connection is established, high bandwidth multicast content originating at the source node is switched to the access module (via well known SVC or SPVC techniques) where it is merged with the CPE to Gateway VCC.
Many of the benefits of multicast are predicated on the notion that certain classes or types of services can be simultaneously delivered to a community of subscribers such as Internet radio, broadcast video or xe2x80x9cnear video on demandxe2x80x9d (staggercast). The techniques embodied in this invention are also applicable to unique service delivery or unicast services such as unique access to content sources, content caches and video on demand.
Internet users now demand music from the Internet in stereo-quality sound and news with a live Web-cast instead of a static headline. Content providers distributing audio and video content, put the contents online and reach a vast and growing user audience via the Web, using technologies, such as Microsoft(copyright) Windows Media(trademark), etc. While such technologies permit content providers to focus on delivering content with moving pictures, stereo sound and features like intelligent streaming, the problem of congestion due to high traffic in the network is compounded. As traffic volumes increase, it becomes increasingly important that the networks deliver appropriate levels of service. Quality-of-Service (QoS) management permits network managers to manage applications that demand high quality, such as audio and video playback, real time voice, etc. particularly in times of inevitable congestion or bottleneck.
Different kinds of application layer proxies, such as Web caches, are widely used in the Internet to improve performance. They increase the efficiency of Internet access by caching FTP text and HTTP objects on selected servers. This means network users can have access to popular Internet material quickly since it is loaded from a cache on or near their local network, rather than a distant Internet site, thereby reducing network traffic and congestion. A technique called TCP splicing provides kernel support for data relaying operations, which runs at near router speeds. Servers using TCP splice can sustain a data throughput twice that of normal servers, with significantly improved packet forwarding performance.
Although deployment of the techniques of VC-merge and TCP splicing have significantly improved the delivery of content to DSL subscribers, there exists a need for providing high quality service for obtaining information from a content provider, while rendering the QoS inherent to the ATM access network transparently to a plurality of CPEs connected to an access module.
An object of the present invention is to provide a method and a system for the efficient provision of content from various content providers to DSL subscribers while supporting transparent QoS capability and bandwidth frugality, using a VC-merge methodology.
In accordance with the present invention, a CPE sends out a request (such as resource ReSerVation Protocol (RSVP), Hyper Text Transfer Protocol (HTTP) or Interior Gateway Multicast Protocol (IGMP)) to a content provider for a particular content. A Service Gateway that serves the CPE intercepts the request and examines it by performing packet snooping. The Service Gateway then determines if the requested content is available from a content provider system that is connected directly to the ATM access network and is capable of originating such content onto the ATM network either as a broadcast, or via subscriber specific service activation mechanisms outside the scope of this invention. In the broadcast or multicast case, the Service Gateway uses ATM proxy signalling to act as the content originator UNI and manipulate the ATM network to add the subscriber to the p2mp tree via a proxy root-initiated join message that contains information specifying merge eligibility, an address of the CPE and a domain identifier. The proxy message will follow the existing routing of the p2mp tree, and will add branches as necessary to reach the access module that serves the CPE. The access module recognizes the merge eligibility of the VCC, terminates the signalling exchange on behalf of the subscriber end system and performs a VC-merge to merge (or PDU interleave) the multicast data into a provisioned Virtual Channel Link (VCL) of the CPE and the content is delivered by the VCL to the designated CPE. In this scenario the access module is required to be merge capable, although other access network nodes are not required to implement this functionality. Since the content is provided using direct ATM connectivity between the hosting platform and the CPE and not though the Service Gateway, congestion at the Service Gateway is reduced. Similarly, as the merge operation eliminates the requirement for the CPE to support call processing directly, QoS is transparently supported.
In the same way that a Service Gateway snoops multicast specific protocol exchanges and manipulates the ATM network accordingly, similar functionality can be extended to content servers (such as video pumps) that are directly connected to the ATM network. The Service Gateway forwards service dialog directly addressed to the content provider using normal routing techniques, and the content provider performs service admission control, etc. The content provider may also create unique service specific VCCs to the subscriber (the VCC Setup message indicating domain specific information and merge eligibility as part of the signaling dialog). In order to perform this function, the server needs awareness that the subscriber is connected to the ATM network. Numerous techniques known to those skilled in the art are available to make this determination (e.g. ATMARP (ATM Address Resolution Protocol) transactions or static configuration based upon subscriber IP address).
As the VCC is routed across the network, any merge capable node encountered inspects a set of pre-existing connections for a subscriber specific connection suitable for merge. If one is encountered, the node proxy terminates the signaling exchange, and configures its switching fabric to merge the new VCC into the existing VCC already going to the subscriber. Note that this is different from the p2mp case in that for p2mp, it is desirable to defer implementing a merge as long as possible when routing a merge eligible VCC. For the point-to-point (p2p), it is desirable to implement the merge as soon as possible when routing a merge eligible VCC.
The advantages of TCP splicing have also been incorporated into the present invention. When a request for a particular Web page is generated from a CPE, a TCP synchronization signal is sent to the Service Gateway, and the Service Gateway sends an Acknowledge (ACK) message back to the CPE acknowledging the request. A TCP dialog is generated from the CPE that contains the HTTP request, which is sent to the Service Gateway. The Service Gateway analyses the request and searches a local cache or cache digest representative of the knowledge available in local caches to determine if the requested Web page is available in the local cache or caches that the gateway has knowledge of. If it is available, the Service Gateway splices the TCP connection to the ATM cache, sending a TCP synchronization signal to a cache server connected directly to the ATM access network, as well as the TCP dialog containing the HTTP request. Upon receiving the HTTP request the cache server sends the requested Web page to the CPE, after setting up a merge-eligible SVC, if required.
The invention therefore permits the transparent provision of QoS to DSL subscribers for content sourced directly from the ATM access network, because the inherent QoS provided in the access network is transparently inherited by the subscriber. The invention also reduces traffic throughout at the Service Gateway, so that overall performance for Internet access is improved.
The role of transparent QoS is to permit highly stateful packet inspection and policy to be performed by Service Gateways while permitting the relatively mundane function of content delivery to be offloaded to simpler platforms subtending the ATM network and taking advantage of capabilities of the ATM network itself, while hiding this complexity from the ATM attached end-system.